26 STUDIES IN FOSSIL BOTANY 



found in the Calamites also, but on the whole, the 

 bundle-system of the latter is less regular and more 

 complicated. Sometimes the bundles of successive 

 internodes are not alternate, but run on in the same 

 straight line. Where this is the case, the forks of the 

 bundle, as we trace it down, instead of attaching 

 themselves to the alternate bundles at the node below, 

 converge again on the other side of the outgoing leaf- 

 trace, so as to form a loop, through which the trace 

 passes out, and the bundle below the loop continues in 

 the same straight line as before. This straight course 

 of the bundles and absence of alternation between those 

 of successive internodes, is specially characteristic of 

 one very ancient type of the Calamarieae, namely the 

 genus Bornia or Archaeocalamites, which occurs in the 

 Lower Carboniferous and the Devonian formation (see 

 p. 70). 



Secondly, we may find a greater complexity in the 

 vascular system. In this case the bundle may run 

 down through more than one internode, and pass on 

 to the second node below (Fig. 8). It follows that 

 here the number of vascular bundles in each internode 

 may be double that of the leaves in a whorl. Where 

 a bundle passes between the outgoing traces at the 

 node, it may either be connected with them by lateral 

 strands or remain free. The former case is illustrated 

 by Fig. 8, from a large and perfectly preserved stem. 

 We may therefore express the general characteristics 

 of the Calamarian vascular system by the statement 

 that the whole arrangement is of the type of Equisetum, 

 but more varied, and sometimes more complex. I may 

 further mention that these variations may even occur 



